sql: remove Engine::scan_index()

This was only used for tests.

src/sql/engine/engine.rs

@@ -61,15 +61,8 @@ pub trait Transaction {
     fn scan(&self, table: &str, filter: Option<Expression>) -> Result<Rows>;
     /// Updates table rows by primary key. Uses a BTreeMap for test determinism.
     fn update(&self, table: &str, rows: BTreeMap<Value, Row>) -> Result<()>;
-
-    /// Scans a column's index entries.
-    /// TODO: this is only used for tests, remove it.
-    fn scan_index(&self, table: &str, column: &str) -> Result<IndexScan>;
 }
 
-/// An index scan iterator.
-pub type IndexScan = Box<dyn Iterator<Item = Result<(Value, BTreeSet<Value>)>>>;
-
 /// The catalog stores table schema information. It is required for
 /// Engine::Transaction, and thus fully transactional. For simplicity, it only
 /// supports very simple operations: creating and dropping tables. There are no

src/sql/engine/local.rs

@@ -1,9 +1,9 @@
 use super::Catalog;
 use crate::encoding::{self, Key as _, Value as _};
+use crate::errinput;
 use crate::error::Result;
 use crate::sql::types::{Expression, Row, Rows, Table, Value};
 use crate::storage::{self, mvcc};
-use crate::{errdata, errinput};
 
 use serde::{Deserialize, Serialize};
 use std::borrow::Cow;
@@ -268,22 +268,6 @@ impl<E: storage::Engine> super::Transaction for Transaction<E> {
         ))
     }
 
-    fn scan_index(&self, table: &str, column: &str) -> Result<super::IndexScan> {
-        debug_assert!(self.has_index(table, column)?, "index scan without index");
-        Ok(Box::new(
-            self.txn.scan_prefix(&KeyPrefix::Index(table.into(), column.into()).encode()).map(
-                |r| {
-                    r.and_then(|(k, v)| {
-                        let Key::Index(_, _, value) = Key::decode(&k)? else {
-                            return errdata!("invalid index key");
-                        };
-                        Ok((value.into_owned(), BTreeSet::decode(&v)?))
-                    })
-                },
-            ),
-        ))
-    }
-
     fn update(&self, table: &str, rows: BTreeMap<Value, Row>) -> Result<()> {
         let table = self.must_get_table(table)?;
 

src/sql/engine/mod.rs

@@ -3,7 +3,7 @@ mod local;
 mod raft;
 mod session;
 
-pub use engine::{Catalog, Engine, IndexScan, Transaction};
+pub use engine::{Catalog, Engine, Transaction};
 pub use local::{Key, Local};
 pub use raft::{Raft, Status};
 pub use session::{Session, StatementResult};

src/sql/engine/raft.rs

@@ -1,4 +1,4 @@
-use super::{Catalog, Engine as _, IndexScan, Transaction as _};
+use super::{Catalog, Engine as _, Transaction as _};
 use crate::encoding::{self, bincode, Value as _};
 use crate::errdata;
 use crate::error::Result;
@@ -187,15 +187,6 @@ impl<'a> super::Transaction for Transaction<'a> {
         Ok(Box::new(scan.into_iter().map(Ok)))
     }
 
-    fn scan_index(&self, table: &str, column: &str) -> Result<IndexScan> {
-        let scan: Vec<_> = self.engine.read(Read::ScanIndex {
-            txn: (&self.state).into(),
-            table: table.into(),
-            column: column.into(),
-        })?;
-        Ok(Box::new(scan.into_iter().map(Ok)))
-    }
-
     fn update(&self, table: &str, rows: BTreeMap<Value, Row>) -> Result<()> {
         self.engine.write(Write::Update { txn: (&self.state).into(), table: table.into(), rows })
     }
@@ -338,13 +329,6 @@ impl<E: storage::Engine> raft::State for State<E> {
                     .collect::<Result<Vec<_>>>()?
                     .encode()
             }
-            Read::ScanIndex { txn, table, column } => self
-                .local
-                .resume(txn.into_owned())?
-                .scan_index(&table, &column)?
-                .collect::<Result<Vec<_>>>()?
-                .encode(),
-
             Read::GetTable { txn, table } => {
                 self.local.resume(txn.into_owned())?.get_table(&table)?.encode()
             }
@@ -380,11 +364,6 @@ enum Read<'a> {
         table: Cow<'a, str>,
         filter: Option<Expression>,
     },
-    ScanIndex {
-        txn: Cow<'a, mvcc::TransactionState>,
-        table: Cow<'a, str>,
-        column: Cow<'a, str>,
-    },
 
     GetTable {
         txn: Cow<'a, mvcc::TransactionState>,